Most animal cells have the ability of secreting cell-derived extracellular vesicles of various sizes and compositions. These extracellular vesicles are found in all biological fluids, including blood, urine, saliva and cultured medium of cell cultures (Loyer X, Vion A C, Tedgui A, Boulanger C M. Microvesicles as cell-cell messengers in cardiovascular diseases. Circ Res 2014; 114: 345-53; Ohno S, Ishikawa A, Kuroda M. Roles of exosomes and microvesicles in disease pathogenesis. Adv Drug Deliv Rev 2013; 65: 398-401).
Extracellular vesicles are membrane structure vesicles with diameters from about 20 nm to about 5 μm. They differ in sizes and compositions and include various species such as exosomes (about 30-100 nm), ectosomes, microvesicles (about 100-1,000 nm), microparticles, etc.
The different types of the extracellular vesicles are distinguished based on their origin, diameter, density in sucrose, shape, precipitation rate, lipid composition, protein marker, secretion type (i.e., whether they are induced by signals or naturally produced), etc. For example, microvesicles are membrane vesicles ranging from about 100 to 1,000 nm with irregular shapes. They originate from the plasma membrane and are known to contain integrins, selectins, markers including CD40 ligand, etc., and phospholipids including phosphatidylserines. And, exosomes are the smallest membrane vesicles ranging from about 30 to 100 nm (<200 nm) with a cups shape. They originate from endosomes and are known to contain tetraspanins such as CD63 and CD9, markers including TSG101 and ESCRT, and lipids including cholesterols, sphingomyelins, ceramides and phosphatidylserines.
The extracellular vesicles reflect the state of the cells (donor cells) from which they are secreted, exhibit various biological activities depending on the cells from which they are secreted, and play an important role in cell-to-cell interactions (cell-to-cell communications) as they transfer genetic materials and proteins between cells.
Prokaryotic cells and eukaryotic cells are also known to secret extracellular vesicles (Camussi, G., Deregibus, M. C., Bruno, S., Cantaluppi, V., & Biancone, L. (2010). Exosomes/microvesicles as a mechanism of cell-to-cell communication. Kidney International, 78(9), 838-848; Bang, Claudia, and Thomas Thum. “Exosomes: New players in cell-cell communication.” The International Journal of Biochemistry & Cell Biology 44.11 (2012): 2060-2064; Kim, D. K., Lee, J., Simpson, R. J., Lötvall, J., & Gho, Y. S. (2015, April), EVpedia: A community web resource for prokaryotic and eukaryotic extracellular vesicles research. Seminars in Cell & Developmental Biology (Vol. 40, pp. 4-7). Academic Press; Kim, J. H., Lee, J., Park, J., & Gho, Y. S. (2015, April). Gram-negative and Gram-positive bacterial extracellular vesicles. Seminars in Cell & Developmental Biology (Vol. 40, pp. 97-104). Academic Press). Meanwhile, lactic acid bacteria, which are the representative beneficial bacteria for human, are bacteria which produce organic acids such as lactic acid or acetic acid by degrading sugars such as glucose or lactose. They are used in preparing fermented foods such as fermented milk, cheese or butter through the fermentation process of producing organic acids from sugars, but there have been few researches on the particular use of extracellular vesicles derived therefrom. The prior art about bacteria-derived extracellular vesicles is disclosed in Korean Patent Publication No. 10-2011-0025603.